Mr Brown, who served as Prime Minister from 2007 to 2010, said: “This declaration is needed now, urgently.

“It is needed now to deal with practical threats to confront gathering dangers and on-the-ground realities of very real week-by-week threats to Jewish communities that demand an unequivocal response and unqualified resolve."

Mr Corbyn has previously backed Labour's decision not to accept the full international definition of anti-Semitism, which includes those who criticise Israel.

He said: “It is unfortunately the case that this particular example, dealing with Israel and racism, has sometimes been used by those wanting to restrict criticism of Israel that is not anti-Semitic.”

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A Labour Party spokesman added: "The Labour Party adopted the IHRA definition of antisemitism in full in 2016 and that has not changed. There is a consultation regarding the Party's Code of Conduct, which will be brought to the NEC this week.

"It would not be right to pre-judge the outcome of that consultation."

The cross-bench peer suggested Jews are more concerned than they had been since arriving in Britain in 1656, comparing Mr Corbyn to Enoch Powell, the Conservartive MP who made the incendiary 1968 'Rivers of Blood' speech on immigration.

Lord Sacks told the BBC One's The Andrew Marr Show: “Anyone who uses the term Zionist loosely, without great care, is in danger of engulfing Britain in the kind of flames of hatred that have reappeared throughout Europe, and is massively irresponsible.

"There is danger that Jeremy Corbyn may one day be prime minister, he is the leader of Her Majesty's opposition, and I'm afraid that until he expresses clear remorse for what he has said and what his party has done to its Jewish sympathisers as well as its Jewish MPs, then he is as great a danger as Enoch Powell was."

A Labour Party spokesman said: "Lord Sacks' comparison with the race-baiting Enoch Powell is absurd and offensive.

"Jeremy Corbyn is determined to tackle anti-semitism both within the Labour Party and in wider society and the Labour Party is committed to rebuilding trust with the Jewish community."